Category: Physics

A:  enlist
B:  opera
C:  repulsion 
D:  none of above

A:  usury
B:  even
C:  entice
D:  uniform

A:  class boundary
B:  class mark
C:  class limit
D:  class frequency

A:  impurities from water
B:  temporary hard from water
C:  heavy water (D2O) from water
D:  permanent hardness from water 

A:  sulphates and chlorides of calcium and magnesiun

A:  an amphoteric compound 
B:   an acid
C:  an base
D:  a positively charged ion

A:  covalent bonding
B:  lonic bonding
C:  hydrogen bonding 
D:  Dipole-dipole interaction

A:  0.0 C
B:  100.0 C
C:  4.5 C
D:  3.98 C

A:  east-west
B:  north-west
C:  north-east
D:  north-south 

A:  40 Hz
B:  50 Hz 
C:  60 Hz
D:  none of above